This invention relates to liquid compositions. More particularly, this invention relates to liquid compositions containing photodecomposable complex salts.
In assignee's copending application Ser. No. 609,898, filed Sept. 2, 1975, incorporated herein by reference, there is described a photocopolymerizable composition containing (a) an organic material containing epoxide functionality, (b) an organic material having hydroxyl functionality, and (c) a complex salt photoinitiator selected from aromatic iodonium complex salts and aromatic sulfonium complex salts. Such photocopolymerizable compositions are very useful for providing cured coatings on a variety of substrates for decorative or protective reasons. Such compositions are typically coated and cured by the manufacturer of the finished article, e.g. beverage can, label stock, coated paper, etc. Each such user of these compositions typically specifies the particular physical characteristics which the curable composition, and the cured coating, must exhibit for his particular application (e.g. color, chemical resistance, coating characteristics, etc.).
Although such photocopolymerizable compositions may be formulated by each industrial user so as to meet his specific requirements, it is much more common for such compositions to be prepared by coating formulators who specialize in the preparation of coating compositions for industrial use. The coating formulators must procure the various necessary ingredients (e.g. base resins, colorants, viscosity modifiers, curatives, etc.) from a number of different sources. With respect to the photocopolymerizable compositions referred to above, it would be highly desirable to be able to supply the coating formulator with a concentrated solution of the complex salt photoinitiator in a form which would permit ready addition to, and compatibility with, a variety of different coating compositions (particularly those which are based on cationically polymerizable materials).
There are, however, numerous requirements which must be satisfied in order for such a concentrated solution of complex salts to be useful for this purpose. For example, the liquid medium not only must be of low viscosity but it must be of a type which will cure into the coating without significant adverse effect on curing rates or physical properties of the cured film. Also, the liquid medium should permit a significant concentration (e.g. at least about 5% at room temperature) of the complex salt photoinitiator to be dissolved therein without deactivation of such photoinitiator over a long period of time (e.g. on the order of one year or more at ambient temperatures). Furthermore, such liquid concentrate must be essentially compatible with the base resin to which it is to be added to make the final curable composition.
The present invention provides a liquid concentrate which is useful for the foregoing purposes.